/*
 * @lc app=leetcode.cn id=380 lang=cpp
 *
 * [380] 常数时间插入、删除和获取随机元素
 */
class RandomizedSet
{
public:
    /** Initialize your data structure here. */
    RandomizedSet() {}

    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
    bool insert(int val)
    {
        if (s.count(val))
            return false;
        s.insert(val);
        return true;
    }

    /** Removes a value from the set. Returns true if the set contained the specified element. */
    bool remove(int val)
    {
        if (!s.count(val))
            return false;
        s.erase(val);
        return true;
    }

    /** Get a random element from the set. */
    int getRandom()
    {
        auto p = s.begin();
        advance(p, rand() % s.size());
        return *p;
    }

private:
    unordered_set<int> s;
};

/**
 * Your RandomizedSet object will be instantiated and called as such:
 * RandomizedSet* obj = new RandomizedSet();
 * bool param_1 = obj->insert(val);
 * bool param_2 = obj->remove(val);
 * int param_3 = obj->getRandom();
 */
